That isn’t guaranteed to work if the relay is used as a crossroads on multiple routes. And I think you mean a coronagraph (https://en.wikipedia.org/wiki/Corona

That isn’t guaranteed to work if the relay is used as a crossroads on multiple routes. And I think you mean a coronagraph (https://en.wikipedia.org/wiki/Coronagraph https://en.wikipedia.org/wiki/Coronagraph: “a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star's bright glare – can be resolved.“). I’m not sure using these to block out the sun is common with very sensitive instruments. Some parts of Hubble can’t look at the sun as doing so would damage them (https://en.wikipedia.org/wiki/Fine_guidance_sensor#Hubble_Space_Telescope_FGS https://en.wikipedia.org/wiki/Fine_guidance_sensor#Hubble_Sp...: “Due to the sensitivity of the FGS they can not be used whilst the HST is pointed within 50 degrees of the Sun.”) Also, of course, blocking out the sun’s light won’t make you see the stars behind the sun.